Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.35	12.513%	$190.5408	$190.54	$190.55	$190.50
Purchase #2	$102.54	10.526%	$113.3334	$113.33	$113.35	$113.30
Purchase #3	$226.51	9.159%	$247.2561	$247.26	$247.25	$247.30
Purchase #4	$39.64	13.860%	$45.1341	$45.13	$45.15	$45.10
Purchase #5	$55.38	3.791%	$57.4795	$57.48	$57.50	$57.50
Purchase #6	$37.32	8.283%	$40.4112	$40.41	$40.40	$40.40
Purchase #7	$216.63	8.274%	$234.554	$234.55	$234.55	$234.60
7 purchase totals =	$847.37		$928.7091	$928.70	$928.75	$928.70